PDA

View Full Version : Did a Supernova Kill the Mammoths?



Fraser
2005-Sep-28, 05:37 PM
SUMMARY: A supernova that exploded 41,000 years ago might have led to the extinction of mammoths, according to researchers at Berkeley Lab. They found ancient mammoth bones peppered with iron-rich grains that had been traveling at 10,000 km/second. These grains might have been emitted from a supernova that exploded about 250 light-years away from Earth. It's also possible that debris from the supernova coalesced into comet-like objects; one could have struck the earth about 13,000 years ago.

View full article (http://www.universetoday.com/am/publish/supernova_kill_mammoths.html)
What do you think about this story? post your comments below.

galacsi
2005-Sep-28, 07:42 PM
This is a quick reply :

Dont undestand anything ! Mammoths bones peppered with iron rich grains ? And the atmosphere didn't stop them ? 41,000 or 34,000 years ago Or a comet 13,000 years ago ?

American science is the greatest ! Nothing compares to it !

cran
2005-Sep-28, 07:54 PM
It does seem a bit out of left field - but if the science is good, then it is another piece to what was an unsatisfactory puzzle. All in all, it seems like they were good times to stay indoors...

galacsi
2005-Sep-28, 08:13 PM
Mister Cran

Please read this :

In fact, tests with shotgun pellets traveling 1,000 kilometers per hour produced no penetration in the tusks. Much higher energies are needed: x-ray analysis determined that the impact depths are consistent with grains traveling at speeds approaching 10,000 kilometers per second.

1,000 km/h is a very slow speed for a shotgun pellet , helium guns can do much better. On the other hand 10,000 km/s is extremely fast , So it mean a little grain of rock can penetrate the atmosphere and not be vaporised ?

cran
2005-Sep-28, 09:16 PM
galacsi-
Mister Cran

Please read this :

In fact, tests with shotgun pellets traveling 1,000 kilometers per hour produced no penetration in the tusks.
The Clovis hunting artifacts were shotguns? :think: Wow!

galacsi-
So it mean a little grain of rock can penetrate the atmosphere and not be vaporised ? Depends upon how 'little' it was when it began penetrating the atmosphere ... but ... your point is?

GBendt
2005-Sep-28, 09:40 PM
Sorry, but this is nonsense!

Why?
if a supernova explodes, its temperature is millions of Kelvin. At such a temperature, iron is not in pellets, its is a plasma. This plasma will move away from the supernova in all directions at very high speed (some 40000 km/s were measured with supernovae). Thus, after thousands of years, the ejected matter will be dispersed over millions of sextillions of square miles. No chance for a pellet to form from such a thinned matter.

Further, even if such pellets had formed, bodies that are travelling through the interstellar medium at a speed that is much higher than the average low speed of the usual interstellar matter will be inevitably slowed down by the numerous collisions with interstellar matter.

And even if no collisions with interstellar matter would have happened and these pellets would burst into the atmosphere at a speed of 10000 km/s, these pellets would break up and would be vapourized in the atmosphere. Because at such a speed, even thin gas is acting like massive armour.

This being so, I dare say no mammouth may ever have experienced any iron pellet penetrating its tusk at a speed of 10000 km/s. The mammouths must have died from something else. I have seen a lot of mammouth tusks in museums and collections, and none of these tusks shows any such pits in their surface.

It is amazing to read an article that shows that their authors have such a little knowledge and understanding of the matter they are writing about ...

If I had read this article in April, I really would have thought it was meant as a joke. But I´m afraid it is not. We are having September now.

Regards,

Günther

ZaphodBeeblebrox
2005-Sep-28, 10:03 PM
All I Can Say, is WOW ....

So, Much Information!!!

And, I Hate to Play, Chicken Little ....

But, Is There a Possibillity of a Shower of Iron-Rich Grains, In a Coupla Dozen Thousand Years; From The Supernova, that Produced, The Crab Nebula?

:shifty:

Bojan
2005-Sep-28, 10:08 PM
It is a joke, isn't it ? :-)

Greg
2005-Sep-28, 10:45 PM
A supernova that recent and nearby should be easy to find by tracing back the orbit of the sun a little bit. That would go along way towards validatnig the theory and I am surprised the authors didn't point out prospective candidate nebulas. A shower of meteorites from various sources could explain these impacts. Perhaps an asteroid broke apart and hit the Earth in various pieces.

Still these ideas might go along way to unravelling some archaeological mysteries, especially the odd migration patterns proposed to expalin the dating of various sites. Before this theory, the lack of colonization of the eastern US and Canada was attributed to persistent continental glaciation. Perhaps that is not the whole story.

ZaphodBeeblebrox
2005-Sep-28, 11:12 PM
A supernova that recent and nearby should be easy to find by tracing back the orbit of the sun a little bit. That would go along way towards validatnig the theory and I am surprised the authors didn't point out prospective candidate nebulas. A shower of meteorites from various sources could explain these impacts. Perhaps an asteroid broke apart and hit the Earth in various pieces.

Still these ideas might go along way to unravelling some archaeological mysteries, especially the odd migration patterns proposed to expalin the dating of various sites. Before this theory, the lack of colonization of the eastern US and Canada was attributed to persistent continental glaciation. Perhaps that is not the whole story.
I Get the Distinct Impression, from The Article, that The Supernove Remnant, has Been Identified.

It Would have Helped, If they'd Said WHICH One, However ...

:shifty:

Fraser
2005-Sep-28, 11:28 PM
I was quite disappointed with the original press release when I wrote my synopsis. I had a zillion questions, but I didn't have time to get them all answered. Maybe I'll contact the researchers and pass along your questions as well.

Cylinder
2005-Sep-29, 12:07 AM
I think some may be misinterpreting the story. According to the author, a supernova ejected an iron-rich cloud. Some on this cloud for whatever reason coalesced into low-density comet like objects which then impacted Earth causing the extinction event.


Firestone and West believe that debris from a supernova explosion coalesced into low-density, comet-like objects that wreaked havoc on the solar system long ago. One such comet may have hit North America 13,000 years ago, unleashing a cataclysmic event that killed off the vast majority of mammoths and many other large North American mammals. They found evidence of this impact layer at several archaeological sites throughout North America where Clovis hunting artifacts and human-butchered mammoths have been unearthed.

From my very limited knowledge, I know that forces such as gravitational perturbation and converging pressure waves can concentrate areas of very limited density into areas where density becomes significant. I'm wondering if this coalescence is believed by the author to have occurred within our solar system. Since more than one object is cited, I would assume the author is suggesting that it was.

The upshot of this article of course is another round of doomsday scenarios, a possible Hollywood B special effects groaner and maybe even small stock gains in companies closely associated with the manufacture of MREs.

kzb
2005-Sep-29, 12:04 PM
I agree this seems completely nuts ! If the mammoths really have been impacted by iron particles at these velocities, 34,000 years ago, the real question is how...?

Is this the same Firestone who jointly edited "Table of Isotopes" (Browne and Firestone)?

dirkbontes
2005-Sep-29, 01:24 PM
The 41,000 and 34,000 year events appear to be direct consequences of the supernova. Did this supernova explode in two different stages that emitted debris at two different velocities? One of them moving 17 percent slower than the other? It is the only possible explanation. Which occurred first? I wonder what I wrote about the supernova mechanism in my book.

dirkbontes
2005-Sep-29, 01:47 PM
if a supernova explodes, its temperature is millions of Kelvin.

That is an understatement.


At such a temperature, iron is not in pellets, its is a plasma. This plasma will move away from the supernova in all directions at very high speed (some 40000 km/s were measured with supernovae). Thus, after thousands of years, the ejected matter will be dispersed over millions of sextillions of square miles. No chance for a pellet to form from such a thinned matter.

I disagree.


Further, even if such pellets had formed, bodies that are travelling through the interstellar medium at a speed that is much higher than the average low speed of the usual interstellar matter will be inevitably slowed down by the numerous collisions with interstellar matter.

Is there that much interstellar matter in 250 lightyears? I seriously doubt that. Besides, that may have been pushed ahead by even faster moving debris. I seem to recall that our local area is in a bubble of low density interstellar material. Could that bubble have been produced by this supernova?


And even if no collisions with interstellar matter would have happened and these pellets would burst into the atmosphere at a speed of 10000 km/s, these pellets would break up and would be vapourized in the atmosphere. Because at such a speed, even thin gas is acting like massive armour.

They presumably were iced up. When the ice evaporated by the entry into the atmosphere, the grains would have been protected from friction by a layer of this evaporated ice. And clearly they did traverse the atmosphere, so saying that to do so is impossible is not correct.


This being so, I dare say no mammouth may ever have experienced any iron pellet penetrating its tusk at a speed of 10000 km/s.

You are wrong. In fact, I was waiting for such or similar evidence of a "13,000"-year comet to be discovered. I expected this, as well as the extermination mechanism, based on my extensive knowledge of mythology and folklore.


The mammouths must have died from something else. I have seen a lot of mammoth tusks in museums and collections, and none of these tusks showes any pits in their surface.

Good for them. They must have died from other causes before the pitted tusks mammoths were struck down. Or do you have written testimonial that the mammoth tusks that you saw date from the same year as the pitted mammoth tusks?


It is amazing to read an article that shows that their authors have such a little knowledge and understanding of the matter they are writing about ...

They appear to have a lot more knowledge and understanding about their discovery than you give them credit for.

Greg
2005-Sep-29, 04:43 PM
I just had a good thought regarding this theory. If indeed small comets were formed within or intercepted by our solar system, then there should still be plenty of them around for us to find. Their composition should be quite a bit different than more ordinary and much older comets. I will see if I can find a reference to an article that proposes what these "comets" would look like.

Greg
2005-Sep-29, 05:02 PM
http://www.spaceref.com/news/viewpr.html?pid=17308

This reference indicates that material can be injected into our solar system from a nearby supernova. If we can find evidence of a very young comet then this would confirm the theory. If not, then the theory would be a long shot.

dirkbontes
2005-Sep-29, 05:20 PM
If we can find evidence of a very young comet then this would confirm the theory. If not, then the theory would be a long shot.

Those supernova grains will have accreted to any comets that orbit the sun. Simply drill a hole in them and you will find them at various depths, each layer being evidence of half a supernova. If we can match them with the second layer and knowing that the two debris rains differ approximately seventeen percent in velocity, we might calculate the distance of each supernova. From the depths of the layers in the comet we might calculate how long ago the supernova exploded, or correlate the age of those layers with the age of the grains.

The idea that these grains - that presumably formed quite near the supernova - would across a distance of 250 light years accrete into a comet is preposterous. They may accrete onto other bodies, but they will not themselves compose a body like a comet.

Greg
2005-Sep-30, 03:58 AM
That is a much more rational thought. The stardust mission will bring back material from the ejected from a comet, which may help answer this question. This is due to reenter in Jan, 2006. Click weblink below for more details.

http://stardust.jpl.nasa.gov/

The Rosetta mission will drop a lander to sample and analyze a comet which is one step better. I included a link to the ESA website below.

http://www.esa.int/SPECIALS/Rosetta/SEMYMPWA6QD_0.html

The best approach would be to scoop out a layer of material from a comet and bring it back. Such missions are under development, I believe. One problem is that there may not be a way to guarentee that a lander will land on a pristine portion of a comet. What if it lands in a crater left behind by a jet where the overlying material containing the most recent supernova grains has been blasted off? I guess the underlying material would still be quite valuable. I guess you have to cross your fingers.

supermc
2005-Sep-30, 09:28 AM
I have never seen a single story unearth so many "experts" lol

Greg
2005-Sep-30, 01:41 PM
Supermc,

I have not seen you post on this story before. I was wondering what your comment was referring to. On second thought, it is probably something that will divert this discussion into something personal and judgemental, so I don't want to know. I will say this much, there is no requirement that someone be an expert in order to post their thoughts on any story. The forum, as I understand it is to educate and promote dialogue about subjects areas related to topics that the moderators choose.

GBendt
2005-Oct-01, 04:15 PM
Hi,

the headline of this article says: Did a supernova kill the mammouths? Evidently, this is a question, not a statement. :think:

And then the article continues: "A supernova that exploded 41,000 years ago might have led to the extinction of mammoths, according to researchers at Berkeley Lab. They found ancient mammoth bones peppered with iron-rich grains that had been traveling at 10,000 km/second. These grains might have been emitted from a supernova that exploded about 250 light-years away from Earth. It's also possible that debris from the supernova coalesced into comet-like objects; one could have struck the earth about 13,000 years ago."

We read: "might have lead", "might have been", "it is possible that", "could have struck". We do not read: "has lead", "has been", "has struck". So far, the factual content of the article is very thin. :think:
The only clear statement given here is that researchers found bones peppered with iron rich particles that had been travelling at 10000 km/s, and in the article we read that this speed was calculated from the impact traces found in the mammouth bones. :exclaim:

The question is, whether supernovae can produce iron-rich particles that can reach the solar system within 7000 years, crossing a distance of 250 light years, and whether such a small particle can cross the atmosphere and can still be powerful enough to hit into a mammouth bone at a speed of 10000 km/s.

Investigations performed by radioastronomic and astrophysical research over decades has revealed that if a supernovae explodes, it does this at extremely high temperatures ( many millions of kelvin), and that it casts ejectae into space at speeds of up to 40000 km/s. At such a temperature, these ejectae are no solid matter, but are a hot plasma which is at a high pressure. Driven by this pressure the cloud of plasma travels out into space, where it expands and reduces its pressure. As it expands, it collides with the cooler interstellar matter that surrounds location of the supernova.
This collision creates a hot shock front that moves through the interstellar matter, collecting that matter and filling up its former location with the matter from the supernova.
According to these scientists, it takes hundreds of thousands of years until the ongoing collision with the interstellar matter has reduced the speed of expansion to a rate equal to that of the average speed of interstellar matter. Then the shock front dies away and cools down, and the matter of the ejectae is able to cool down to some thousand kelvin.

Only that cool, the matter is able to do the transition from its plasma state to form atoms. At that state, the matter ejected from the supernova may fill a sphere with a radius of many light years. That is a huge volume, and the density of the matter within this volume is extremely low.
It takes another hundred of thousands of years until micron-sized dust particles may start to grow in this thin matter, and it takes further millions of years for these particles to create larger particles, which break up again, as they collide with each other in the long course of time.
It takes extremely long time to form bodies from an environment which contains only a few atoms per cubic inch. Thus, the estimation of 7000 years for this process, as proposed by the researchers, is far too low.

The matter ejected from a supernova explosion requires much more time to cool down and form particles, if it will form any particles at all.

Physicists who are doing research on the conditions at which comets develop are in agreement that it may take billions of years for a comet to form, as the density of matter is low in space.
I never read a report on or heard of a comet that may have grown in a short time. It very much looks like physics simply do not allow this.

How could it then be that the berkeley resaerchers found layers of unusual matter which are from another celestial body?
At rare occasions a small asteroid or a comet may collide with our earth, and has done so in the past. Usually, such a body breaks up in the atmosphere in a blast. If the body is large and fast enough, this blast reaches the effect several megatonnes of TNT, which may throw down millions of trees and kill millions of animals, and men. Remember the Tunguska event a century ago. All what was left of the impactor who caused this desaster was fine dust, burnt into the charred tree trunks, and which could be traced as being "not from earth" because of its special isotopic composition.
Only very compact and massive bodies of iron or iron-rich rock may crash into earth, and then this blast takes place on the ground, creating an impact crater. Fortunately, this does not happen often. :dance:

And for the speed of 10000 km/s:
If a particle enters the atmosphere at a speed, pressure will build up at the front of this particle. The higher the speed, the higher the pressure. The higher the pressure, the higher is the temperature caused by the pressure, and the greater is the force working against that moving particle, and thus it is braking down the particle. If the pressure is too high, the resulting force can be too much for the structure of the particle to stand it, and then the particle breakes up.

A speed of 10000 km/s means 36 million kilometers per hour. It is 1285 times the speed of the space shuttle. We were shown in a cruel way that a space shuttle can be ripped apart by the atmosphere while traveling at 6 km/s. Imagine what the atmosphere would do to a particle which travels through it at a speed 1285 times higher.
No particle which travels at a speed of 10000 km/s into the atmosphere will be able to reach the ground intact, and still at this speed!

The average density of the interstellar medium is some 0,1 milligram per million cubic kilometers, if I recall the figure right. If you calculate the volume of a sphere which has a radius of 250 light years, you get an idea of the mass of the interstellar matter which this sphere may contain.
In the solar system, the average density of the interplanetary matter is given as one gram per million cubic kilometers.
Whatever is ejected from a supernova to reach earth, will have to pass through the matter which is between these two bodies.

regards,

Günther

antoniseb
2005-Oct-01, 04:50 PM
This is such a strange story. I'll be interested in seeing what the authors tell you Fraser.
Why, for example, was an SN able to take out the mammoths, but not our ancestors?
Like ou say there are many questions that should spring up, but this article doesn't begin to answer.

snowflakeuniverse
2005-Oct-03, 09:12 PM
Where is this supernova now?

A supernova leaves debris expanding across space at near relativistic speeds and over time such debris would be spread over a vast region of space that should be observable as a nebula. Where is this cloud now?

The answer to this “observation problem” can be explained by my Uniform Expansion theory. The effect of gravity was more powerful in the past, which allows much smaller amounts of mass to form stars. The increased effect of gravity and the faster “clock rates” of the past caused stars to evolve much faster than they do presently which resulted in the formation of many “miniature” supernovas. For example, when the universe was a few million years old, the mass currently found in our solar system would have been enough to form a few hundred “stars”.

The math for this was posted in the “outside the mainstream” forum in which I explained the energy production from quasar without resorting to a super massive black hole.

Snowflake